Does a voltmeter (using the cigarette lighter plug) help us determine the health of the car battery?

[ninjababez]

there can be tons of voltage drop depending on where you measure the voltage during cranking that's why the batt analyzer is clipped directly to the battery during testing

failed to mention that the next day, amaron tech prior to replacing the 3k batt tested it with the same result 8v while cranking and CCA daw is really low (did not get the numbers).

[oj88]

sa stock cig port lang bro

Exactly. Hindi ba namamatay cig socket ng car mo pag nag-start ka?

[ninjababez]

Exactly. Hindi ba namamatay cig socket ng car mo pag nag-start ka?

i wish i could borrow my old 12v voltmeter from bong baron and my vios from my cousin to prove this

[dr. d]

hindi naman namamatay ang cig socket when starting. at least, not in my car.
but the electricity flowing to it can get pretty low, depending on how strong the battery is, how many other accessories are in play, and how thick the wiring and grounds are...

if one plugs an incandescent bulb accessory into it and then start the engine, the bulb dims but not completely extinguishes. some auto mechanics even have a regular but specially-chosen bulb, for precisely this! "doc, pag hindi na umilaw yung filament ng bumbilya, ibig sabihin mas mababa na sa X volts ang nariyan."

a digital gadget that requires constant voltage, may shut down when the voltage powering it gets too low.. but an old electromechanical meter will just move its needle to the low reading, which is how it reads low voltage, which is what we wanted to measure in the first place.

[Flipo]

I have scangauge 2. It connects to the obd port and gets power there. It reads out voltage while cranking. Sooo. Obd has power during cranking.
Maybe elm327 with Torque app can help read it out during crank?

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^if you want real time voltage reading use an oscilloscope

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If OBD can get data while cranking it means the port is still powered.

It reminds me in the 80's when we used the digital storage scope to capture and record the pulses of an equipment in order for us to adjust it later to the correct peak to peak voltage required.

[SoleusBB]

Teka, question na rin.

Perhaps using an old fashioned battery hygrometer will give a better indication of battery health? Medyo tedious nga lang, kasi you'll have to draw battery acid into the tube for every cell.

I'm not sure if applicable nga lang ito sa sealed type na maintenance free... but I think some maintenance free batteries have covers designed to be pried off with a flathead screwdriver.

[oj88]

If OBD can get data while cranking it means the port is still powered.

It reminds me in the 80's when we used the digital storage scope to capture and record the pulses of an equipment in order for us to adjust it later to the correct peak to peak voltage required.

There's a B+ pin on the OBD port that is always connected to the battery. That's why it does not shutdown when you crank the engine.

[oj88]

hindi naman namamatay ang cig socket when starting. at least, not in my car.
but the electricity flowing to it can get pretty low, depending on how strong the battery is, how many other accessories are in play, and how thick the wiring and grounds are...

if one plugs an incandescent bulb accessory into it and then start the engine, the bulb dims but not completely extinguishes. some auto mechanics even have a regular but specially-chosen bulb, for precisely this! "doc, pag hindi na umilaw yung filament ng bumbilya, ibig sabihin mas mababa na sa X volts ang nariyan."

a digital gadget that requires constant voltage, may shut down when the voltage powering it gets too low.. but an old electromechanical meter will just move its needle to the low reading, which is how it reads low voltage, which is what we wanted to measure in the first place.

We have the same vehicle, except for the transmission.

This is how my D4D Innova behaves when turning the key from OFF/LOCK > ACC > ON > START > ON

While the engine is cranking (ignition key on START), the ACC line experiences a power cut-off. My Echo Dot, and even the HU goes blank and reboots.

If you notice, the backup sensor switch indicator LED and the climate control didn't even 'blink' when the starter was engaged. This indicates that they are wired with the ignition "ON" position and is not affected by the ACC line cut-off.

[dr. d]

i wish i could borrow my old 12v voltmeter from bong baron and my vios from my cousin to prove this

i have two VOMs, here at home. one digital-display, one analog-display.
but tinatamad akong mag-dissect ng cig lighter plug, just to be able to connect 'em.
and i'm a bit uncomfortable, sticking them probes inside the cigarette lighter socket, while i use my third hand to twist the key...

[oj88]

i have two VOMs, here at home. one digital-display, one analog-display.
but tinatamad akong mag-dissect ng cig lighter plug, just to be able to connect 'em.
and i'm a bit uncomfortable, sticking them probes inside the cigarette lighter socket, while i use my third hand to twist the key...

Allow me.

That's fairly conclusive. Power is temporarily removed from the ACC line whenever you crank the engine. So a dashboard voltmeter that's tapped to the cig socket is useless to measure the battery voltage while cranking.



Note: My analog meter is 'zeroed' for when it is lying down on my bench. Hence, the needle isn't aligned to zero (0) with no input while propped up in this test.